Using Electronic Navigational Chart for 3d Bathymetric Model of the Port of Naples

Abstract

Abstract. Nautical charts generally report fundamental knowledge for the safety of navigation. This information also includes sea depth data reported as depth points or contour lines, which can be used to build a 3D model of the seabed. However, there are different interpolation methods for creating digital depth models, and there is no way to know in advance which of them is the best performing. The aim of this work is to compare different spatial interpolation methods applied on a dataset concerning the seabed of the Port of Naples (Italy) and extracted from the Electronic Navigational Chart (ENC) produced by the Hydrographic Institute of the Italian Navy, in scale 1:10.000. Four deterministic interpolation methods, i.e. Inverse Distance Weighting (IDW), Global Polynomial Interpolation (GPI), Local Polynomial Interpolation (LPI), Radial Basis Function (RBF), and two stochastic interpolation methods, i.e. Ordinary Kriging (OK) and Universal Kriging (UK), are applied using Geographic Information System (GIS) software. Since each method requires to set specific parameters and different options are available, e.g. the order of the polynomial function for GPI and LPI, or semi-variograms for OK and UK, twenty-three models are generated. The result quality is evaluated by Leave-One-Out cross-validation and the statistics of the residuals produced by each interpolation method in the measured points are compared and analysed. The experiments confirm that the stochastic approach is more versatile compared to deterministic approach and can produce better results, as it is testified by the great performance of the Ordinary Kriging, which produces the most accurate 3D models.

Statistical Assessment of Some Interpolation Methods for Building Grid Format Digital Bathymetric Models

“…RBMF was the significantly performing interpolation method, achieving a mean NMAD below 0.3 m. It was clo followed by OK, which returned a mean NMAD value of 0.35 m. In contrast, both G and UK performed significantly worse, obtaining mean NMAD values of 0.75 m an m, respectively. These results agree with those obtained by Alcaras et al [16], confirm the good performance of OK with the so-called stable semi-variograms among the g of stochastic interpolation methods. Similarly, RBMF proved to be an outstanding efficient method within the group of deterministic interpolators.…”

“…In these cases, the vertical accuracy achieved for depth data took values, in terms of RMSE, of 1.41 m for Landsat [13], 0.518 m for the log-band ratio method and 0.35 m for the OBRA method working on QuickBird imagery [14], or 3.71 m for WorldView 3 [15]. Furthermore, there are several studies in the literature in which electronic navigational charts (ENC) are used as a source to extract bathymetric information [16].…”